5 Space Launch System Mobile Launcher Modal Pretest Analysis 39 Fig. 5.4 SLS on mobile launcher at launch pad (l) and Umbilicals (r), (from http://NASASpaceFlight.com) Fig. 5.5 SLS mobile launcher rolling out to launch pad 39B, September 2018 (l) and CT-2 rolling on crawler way (r) noise effect the first three resonance speaks the most because the ML shaker force levels are lower in this frequency range due to their stroke limitations. 5.3 Residual Vectors and Accounting for Compliance Contribution of Out-of-Band Modes Residual vectors are required to accurately account for the compliance contribution of the out-of-band modes in the pretest analysis. Including elastic body modes up to four times the frequency range of interest were retained, but without residual vectors, erroneously showed the shaker and drop hammer drive points were less compliant (i.e. stiffer) than what they actually are, which in turn lead to the erroneous conclusion they were able to excite more modes then they actually could. Figure 5.7 shows the effect of including residual vectors on the D/F drive point FRF at two locations, one that is very stiff and the other that has significant compliance. This shows that even if the frequency range of interest is quadrupled, but residual vectors are
RkJQdWJsaXNoZXIy MTMzNzEzMQ==